Field of the Invention
The present invention relates to an automatic transmission fluid warmer coolant circulation system and design method thereof, and more particularly, to an automatic transmission fluid warmer coolant circulation system and design method thereof capable of preheating Automatic Transmission Fluid (ATF) in the low temperature condition of 70 degrees or less of the engine coolant.
Description of Related Art
In recent years, due to global high oil prices and CO2 regulation, as fuel efficiency improvement and eco-friendly property have been treated as key items in the vehicle development, automobile manufacturers have devoted all its efforts on a variety of technical developments for fuel reduction.
Among such technologies, an ATF warmer coolant circulation system is a way of improving the fuel efficiency by further improving the transfer efficiency of an automatic transmission. The ATF warmer coolant circulation system is configured to apply an ATF warmer in which heat-exchange takes place by the circulation of ATF and engine coolant, install a bypass valve at a connection portion between an ATF line and an engine coolant line, and connect the bypass valve with a controller. Therefore, in the ATF warmer coolant circulation system, the ATF of a low temperature heat-exchanges with the engine coolant of a high temperature through the bypass valve opened by the control of the controller at a preset engine coolant temperature such that the temperature rise in the ATF takes place, and also, the elevated temperature ATF is circulated into the automatic transmission, whereby the transfer efficiency of the automatic transmission is improved. At this case, the engine coolant is circulated in the order of an engine→a heater core→an ATF warmer→the engine. Herein, “→” refers to the flow direction of the engine coolant.
For this, the ATF warmer coolant circulation system applies the engine coolant temperature of about 70° C. or more as an operation temperature, a controller opens the bypass valve at 70° C. or more but closes the bypass valve at 70° C. or less based on the engine coolant temperature of about 70° C. The controller applies an engine Electric Control Unit (ECU) or a Transmission Control Unit (TCU).
However, the conventional ATF warmer coolant circulation system applies the dualization of the ATF line and the engine coolant line, and the flow control valve type bypass vale in order to improve the fuel efficiency and maintain heating performance under the low temperature condition, such that it is bound to have system limitations which should make the engine coolant temperature of about 70° C. or more as the operation temperature even though the transmission transfer efficiency goes to the maximum at the ATF temperature of about 60° C. or more.
In particular, the bypass valve of the conventional ATF warmer coolant circulation system is installed at a front end of the ATF warmer, such that the heater core side flow rate is increased by the engine coolant not passing through the ATF warmer when the bypass valve is closed at 70° C. or less, whereas the ATF temperature rise is delayed when the bypass valve is opened at 70° C. or more due to the ATF preheating impossibility whereby it inevitably lacks the performance for the fuel efficiency improvement due to the low transmission transfer efficiency.
Therefore, in the conventional ATF warmer coolant circulation system, the improved technologies that can maintain heating performance in a low temperature condition and properly implement the fuel efficiency improvements through the transmission transfer efficiency improvements by rapid temperature rise of the ATF, have been required.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.